Ganged function potentiometer



April26, 1960 c, WOLFE EIAL 2,934,734

GANGED FUNCTION POTENTIOMETER Filed June 14, 1957 v 3 Sheets-Sheet 1 INVENTORS CHARLES M. WOLFE 8 JOSEPH M. GA/LL/OT; JR.

c. M. WOLFE ETAL 2,934,734

GANGED FUNCTION POTENTIOMETER April 26, 1960 Filed June 14, 1957 3 Sheets-Sheet 2 INVENTORS CHARLES M. WOLFE 8 JOSEPH M. GA/LL/OT; JR.

April 26, 1960 c. wo ETAL 2,934,734

GANGED FUNCTION POTENTIOMETER Filed June 14, 1957 3 Sheets-Sheet 3 JOSEPH M. aa/LL/oz an.

- INVENTOR. OHARL 53 M. WOLFE a United States Patent GANGED FUNCTION POTENTIOMETER Charles M. Wolfe, Glendora, and Joseph M. Gailliot, Jr.,

Chino, Calif., assignors to General Dynamics Corporation, San Diego, Calif, a corporation of Delaware Application June 14, 1957, Serial No. 665,706 3 Claims. (Cl. 338176) This invention relates to electrical measuring, controlling, and/or generation apparatus of the variable resistance or potentiometer type and more particularly to such apparatus in which a plurality of electrical resistance or conducting elements may be simultaneously engaged by contact-making members for producing a plurality of electrical signals.

Potentiometers, programming devices, or function generators operating from a single shaft or input for producing a plurality of electrical conditions simultaneously are not in themselves new. It is conventional in such devices to utilize variable resistances or conductive elements, either wire-wound or conductive films, on a core of non-conductive material. These elements can be constructed to produce linear or non-linear functions or have insulated portions for on-off switching. In these devices it is also well known to utilize a plurality of the conductive elements spaced around a threaded shaft upon which is mounted a travel block axially movable upon rotation of the shaft. Attached to the block is a plurality of wiper arms making electrical contact with the individual elements. The shaft may be rotated at a constant or variable rate or may be controlled in a predetermined manner by one of the contacted elements as desired.

Weather used individually or by combining the best features of several devices into a single unit, these prior art devices are inadequate in numerous applications or have certain important disadvantages that reduce their eifectivity. For example, when subjected to environmental conditions, such as shockand vibration, that present day airborne devices must withstand, such prior devices were found unreliable with respect to accuracy as well as general operability. In many applications the size and space requirements demanded by prior devices prevented their use, and efforts simply to reduce the relative size of the various components comprising the devices compromised various functional characteristics. Furthermore, such devices heretofore did not allow convenient replacement, removal or adjustment of individual function elements without disturbing other elements of the unit, the functional elements were not interchangeable, nor were they easily accessible for maintenance and repair.

The present invention comprises basically two sections; alead screw and travel block section and a functional element section, which may include either one or two functional elementunits. The lead screw may be actuated mechanically or by a motor, as illustrated in the drawings, to move a threaded travel block ,axially along the screw. Mounted on the travel block is a plurality of wiper contacts for contacting the elements in the functional element units. The functional elements may be either wire wound or conductive coated cores with one edge exposed for contact by the wiper arm. Adjacenteach of the functional elements is an electrical return path completing each individual circuit. The elements are designed so as to be installed side by side and capable of individual adjustment. They may be adjusted,

ice

ference with other elements, the lead screw, or travel block. Due to their shape, size, and arrangement within the unit, a multiplicity of elements occupy but a very small space. Each functional element is rigidly fixed within the unit and means are provided for withstanding shock and preventing vibration between the travel block and the functional elements.

Due to its modular construction, size and weight, its accuracy, ruggedness and reliability, and its convenience of adjustment and interchangeability, the present invention may be used in supersonic aircraft or guided missile control systems. By proper selection of the functional elements, the present invention may also be used as a program timer in controlling the on-off times and relative timing operations of a multiplicity of circuits, for coordinating the operation of electrical equipment and automatic devices, and for use in actuating computers and as a precision sensing unit for feedback control inautomatic control appliactions.

It is therefore an object of the present invention to pro-- vide improved electrical apparatus for producing a p1urality of electrical functions.

Another object of the present invention is to provide a potentiometer of modular construction having a plurality of functional elements for simultaneously control- 'ling current flow in a plurality of circuits.

Another object is to provide an improved device for producing both step or timing functions and variable resistance functions.

Another object is to provide a device in which the function generating section can be conveniently removed from the lead screw and travel block section.

Another object is to provide a multiple potentiometer in which the function generating elements may be individually removed, zero adjusted or aligned without disturbing other elements.

Another object of the present invention is to provide a device of modular construction in which a plurality of wafer-like function generating elements are supported in side by side arrangement within a conveniently removable supporting frame.

Another object of the present invention is to provide a precision, ganged potentiometer type device capable of withstanding severe environmental conditions.

Another object of the present invention is to provide a multiple potentiometer and programming device offering a wide variety of programming selection, yet is small, lightweight, rugged, and economical to manufacture.

Other objects and features of the present invention will be readily apparent to those skilled in the art from the following specification and appended drawings wherein is illustrated a preferred form of the invention, and in which:

Figure 1 is a perspective view illustrating the assembly of one embodiment of the invention Figure 2 is a cross-sectional view along the lines II-II in Figure l; I

Figure 3 is a cross-sectional view along the lines III-III in Figure 2;

Figure 4 is a perspective view of the travel block upon which contact wiper arms are mounted;

Figure 5 is a perspective view of one functional element ready for assembly; and

Figures 6, 7 and 8 show other types of functional components.

Figure 9 is a perspective view illustrating an interchangeable functional element in which the conductive element is discontinuous for generating on-off conditions.

7 Referring now to the drawings wherein like numerals designate like parts throughout the several views, Figure;

- 1 shows an assembled unit including the lead screw and connected to the functional elements, enter small recesses 17 in the element sections just inwardly of cover plates 18thereby allowing the cover plate to be removed without removing the leads. The type of motor 14 is a matter of choice depending upon the application of the device. Motor 14 may be a synchronous motor where substantially constant speed is desired or may be of a type used extensively in automatic control applications and commonly termed a servo motor. Motor 14 may be incorporated within a servomechanism and driven by an input signal which corresponds to some physical condition such as shaft position, pressure, speed, etc. However, it should be understood that motor drive 14 is not an essential element of the invention and it is contemplated that any means of suitably advancing the lead screw will sufiice. It will also be apparent that the lead screw, to be described hereinafter, need not necessarily be a threaded member but may be a shaft carrying the travel block and capable of translational movement.

As shown in Figure 2, the motor 14 drives lead screw 19 through friction clutch 21. The friction clutch provides for slight misalignment of the lead screw 19 and motor 14 and is normally adjusted in end thrust to slipat some torque value less than the stall torque of the motor 14, thus reducing hazard of damage during set up and adjustment. The clutch will also slip when the travel block reaches the end of the screw and the motor 14 continues to turn. An internally threaded collar 22 on motor 14 is threaded onto its associated collar 23 on the end wall 24 of the lead screw and travel block frame 11 in connecting the motor 14 for driving screw 19. ring 26 seals the connection against foreign matter.

Lead screw 19 is rotatably mounted on bearings 27 and 28 in centrally positioned apertures in the ends of frame 11. Bearing 27 shoulders against flange 29 on frame 11 and abuts the end of the threaded portion of screw 19 to limit its inward movement. After bearing 28 is seated over the other end of the screw, plug 31 is threaded into the aperture over the end of the screw. Plug 31 has contact surfaces 32 for loading bearing 28 which is shouldered against the end of the threaded portion of the screw. When plug 31 has been inserted, its surface 32, bearing 28, hearing 27 and flange 29 hold screw 19 against longitudinal movement in response to shock and vibration. The bearings, of course, prevent movement of the screw in any direction normal to its axis.

Mounted on lead screw 19 for longitudinal movement is a rectangular travel block 33 connected tofollower nut 34. As shown in Figures 3 and '4, the nut 34 has an adjustable diameter for varying the tightness of fit over the threads of screw 19. The adjustment compensates for wear and is such that case of travel ispermitted yet chatter, play or backlash is prevented.

Means for preventing rocking, oscillation or vibration of travel block 33 is provided in the form of channel 36 and adjustable channel 37 incorporated in wall members 38 and 39, respectively, together with travelers 41 and 42, which are connected to travel block 33 and arranged for sliding engagement with surfaces 43 and 44. Member 46 includes a projecting portion 47 and when member 46 is attached to frame wall 39 by screws 49 through enlarged holes in the plate which provide adjustment, one surface of portion 47 forms the adjustable channel surface 43. Adjusting screws 48 are provided which aid in establishing surface 43 in bearing relationship with traveler 42. When adjusting screws, 48 are tightened down, projecting portion 47 is forced downwardly thereby adjusting the height of channel 37. Surface 43 forces traveler 42 downwardly and traveler 41 upwardly against surface 44. Thus, rocking, vibration and oscillation of travel block 33 is materially reduced as lead screw 19 reverses its direction of rotation, changes its angular velocity or is subjected to external environmental conditions. It has been found to be important to prevent spurious mechanical movements of the travel block since the brush pressure of the various individual brushes is affected, electrical signals may be modified or serious electrical noise problems may be generated. Travel block 33, which carries the brushes, is free to travel along the lead screw but is restrained against rotation, oscillation or misalignment.

As mentioned hereinbefore and shown in Figures 1, 2 and 3, associated with the lead screw and travel block section 11 is a removable function element section which in this embodiment comprises units 12 and 13 carried on opposite sides of section 11. Units 12 and 13 serve to house and rigidly support functional elements 51 in the desired relationship to the movable travel block 33, and each unit is arranged to be readily removable and interchangeable with other units without disturbing the travel block or adjustment of the functional elements. Thus, a complete unit comprising any desired array of functional elements can be easily and quickly substituted for any other unit or, where desired, one or more individual functional elements may be removed or interchanged. Furthermore, in the present invention access to the travel block section 11 and the brushes is also readily provided by simply removing one of the detachable functional element units.

Although units 12 and 13 are shown as being rectangular, it will be apparent that the particular configuration is a matter of choice. They could as well be annular provided proper adjustment is made in the mating travel block section 11. Units 12 and 13 have an opening therein for housing the functional elements and include flange portions 52 and 53 extending across the ends for supporting the functional elements 51. Suitable spacing has been provided between flanges 52 and 53 to allow the functional elements 51 to be received therebetween and the supporting members associated with the functional elements to be supported by the flanges. Functional elements are suitably attached to the unit, such as by-screws 54. Means in the form of elongated slots 56 are provided at each end of the functional elements to provide longitudinal adjustment of the elements 51 relative to one another or with respect to wiper arms 57 mounted on travel block 33, which serve to provide moving contact with each of the functional elements 51. The adjustment herein provided serves to compensate for any manufacturing errors in the particular parts, allows the functional elements to be individually adjusted for zero setting and provides means for varying the program timing, as desired, by adjusting the position of the functional elements relative to the contacting members on the travel block.

Figure 5 is a perspective view of one of the elements 51 readyfor assembly. Each element consists of two parts. A supporting member, which has the same configuration regardless of the nature of the core that it carries, and the core 58 over which is wound microfine wire 59. The windings are insulated by the varnish coating on the wire 59. However, the windings are bare and exposed for contact with wiper arm 57 along the lower edge 61. The core 58 is preferably of a suitable plastic material with an edge preferably of a vitreous material for presenting a smooth wiper arm contact surface over which the wire is wound. Such a core is further described in copending application No. 610,959 for a Potentiometer Element, filed September 20, 1956, now Patent No. 2,878,349.

Core 58 is attached to a supporting member 62by bonding, gluing or other'suitable means. Member 62 is an itegral unit and includes a top surface 63, end

members 64 and 66 and a side wall 67 to which the functional element core is attached. The elongated adjustingslotssfi are provided in the endmembers 64 and 66, the lower surfaces of which aresupported withrn nnits 12 and 13 by flanges 52 and 53 as described hereinbefore. I Terminals 68, 69 and 71 are electrically interconnected with the core windings and return path. Core 5 8, with its associated functional winding, is fixedly attached to side wall 67 which has an edge surface 72 arranged to be adjacent to and parallel with core edge 61. Edge surface 72 is made electrically conductrve and is interconnected with appropriate terminals 68, 69 and 71 to form a return path Electrically conductive edge surface 72 and core edge 61 are aligned in the same plane, as well as being parallel, so that brush or wiper pressure may be accurately controlled.

'As showninFigure 4 the wiper arms 57 have two resilient fingers 73 and.74 each for contacting both edges 72 and 61., Thus, electrical continuity is provided from oneof the terminals, through winding 59, wiper arm 57, side edge; 72 and another of the terminals. It should be noted, that neither screw 19 .nor travel block 33'are in the circuit path. 1

Figures 6 and 7 are perspective views of core 58 having modified shapes. When the wire is wound on these cores, its conductivity or resistance is not a linear function of length but has a resistance characteristic determined by the particular configuration. These cores may be attached to supporting members 62, as hereinbefore described, and operatively installed within the functional element units 12 and 13.

Figure 8 is an exploded view of another functional element which shows in more detail the construction of core 58 and supporting member 62 for use in functional element units 12 and 13. This element when installed in unit 12 or 13 serves to develop on-ofi, or switching, functions. Conductive elements 76 are positioned at selected positions on core 58 and are preferably made flush with edge 61 of the core. Electrical connections with elements 76 are necessary, and in this embodiment elements 76 are provided by conductive bars mounted to the core. The ends of elements 76 extend through surface 63 of support member 62 to form terminal connections. Figure 9 illustrates another type of on-off switch element that may be attached to one of the supporting members 62 and utilized in the functional element units. Here, a wire 77 is used as a conductive element, and at some desired position along edge 61 the wire is broken to form a gap. In this embodiment the intermediate portion forms no electrical function but serves as a spacer to maintain a substantially constant edge line upon which the brush rides. In addition, a suitable insulating material may be inserted in the gap thereby further improving movement of the brush associated with travel block 33 as it travels along the surface.

Thus, it may be seen that a variety of electrical conditions can be produced by appropriate design of the windings or conductive patterns associated with standardized core elements 61. These core elements are appropriately attached to standardized supporting members 62 to provide a thin, wafer-like electrical component. These components are arranged in side-by-side relationship within the functional element unit of the present invention. The functional components are supported in proper position, alignment and adjustment by flanges 52' and 53. Accurate alignment of edges 61 with respect to the movement of brushes 73 and 74 carried by travel block 33 is accomplished by making suitable adjustments in the undersurfaces of end members 64 and 66 of the supporting member 62, which are supported by flanges 52 and 53.

All functional components, regardless of the electrical function generated, are standardized into thin, rectangular modular units which are supported in juxtaposed position within the detachable mounting frame, which is accurately positioned with respect to the travel block unit. It will be apparent that functional elements having a thickness greater than the standard modular units 6 may be effectively used. It has been found that functional elements having modular widths of two or three times that of the standard units may be used for the purpose of accommodating a plurality of larger resistive elements or for mounting fixed resistors in switching For use with functional elements having applications. larger modular widths the contacts which engage the brushes may bealigned for contact by one or more of the brushes 57 and certain ones of the brushes 57 may be interconnected as desired. The functional components are held in proper alignment and adjustment by the mounting frame with their contacting edges being supported in substantially the same plane. Each of the plurality of functional components is supported withinthe functional element mounting frame to allow any individual'component to be removed, replaced or adjusted without disturbing other components or the travel block. In accordance with the present invention, an unlimited number of electrical functions can be produced by a single unit'simply byincorporating the de-,

sired number of functional elements. With its reliability, ruggedness and convenience of interchangeability and adjustment, the present invention may be used in aircraft or guided missile control systems for producing any number of desired output signals. Simultaneously, by the selection of appropriate elements, the same unit can also act as a program timer, can generate desired electrical signals for purposes of control and can further produce functional signals for any number of other desired applications.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

We claim:

1. Potentiometric apparatus comprising a frame member, a travel block supported within said frame member and arranged for translational movement therewithin, a lead screw rotatably mounted in said frame member, said travel block being threadedly engageable with said screw for axial movement thereon upon rotation of said screw, said frame member having an aperture in one end thereof, a first bearing in said aperture, said screw having an end portion extending through said bearing and a shoulder portion abutting said first bearing, said frame member having a second aperture in the end opposite said one end, a second bearing in said second aperture having an end portion of said screw therein and a shoulder portion thereof abutting thereagainst, and adjusting means for moving said second bearing inwardly against said screw to maintain said screw in axial alignment against said first bearing and to position said first bearing against said flange, a plurality of wiper elements supported by said travel block, a functional element housing attached to said frame member, a plurality of functional elements supported within said functional element housing, each arranged in conductive relationship with one of said wiper elements, said functional element housing being mounted on said frame member for removal of said plurality of functional elements as a unit.

2. Potentiometric apparatus comprising a frame member, a travel block supported within .said frame member and arranged for translational movement therewithin, a lead screw rotatably mounted in said frame member, said travel block being threadedly engageable with said screw for axial movement thereon upon rotation of said screw, said frame member having an aperture in one end thereof, a first bearing in said aperture, said screw having an end portion extending through said bearing and a shoulder portion abutting said first bearing, said frame member having a second aperture in the end opposite said one end, a second bearing in said second aperture having an end portion of said screw therein and a shoul- 7 der portion thereof'abutting thereagainst, and adjusting means for movingsaid second bearing inwardly against said screw to maintain said screwin axial alignment against said first bearing and'to position said first bearing against said flange, said adjusting means comprising a plug, means for threadedly engaging said plug in said second aperture for axial movement therein, said plug having contact means engageable with said' second bearing for moving said second bearing inwardly, a plurality of wiper elements supported by said travel block, a functional element housing attached to said frame member, a

plurality of functional elements supported within said functional element housing, each arranged in conductive relationship with one of said wiper elements, said functional element housing being mounted on said frame m'ent therewithin, moving means connected with said travel block for moving said blockwithin said frame; channels in said side-walls, one of'said channels having-an adjustable height, roller means on the outer ends' ofsaid block engageable with the upper surfaces of said channels to prevent upward movement of said block; said" moving means being mounted on said frame member for preventing downward movement of-said block;

References Cited in the file of this patent UNITED STATES PATENTS 439,660 Holmquist Nov. 4, 1890- 2,493,000 Linsley Jan. 3, 1950 2,706,230 Bourns et a1. t Apr. 12, 1955 2,759,080 Bourns Aug. 14, 1956 2,777,925 Stolz Jan. 15, 1957 2,777,926 Bourns "Jan. 15, 1957 2,850,607 Bourns Sept. 2, 1958- 2,857,497 Bourns Oct. 21," 1958" 

